1). Field of the Invention
This invention relates to a panoramic imaging arrangement of the kind capable of capturing, focusing, correcting aberrations and otherwise manipulating light received from a 360xc2x0 surrounding panoramic scene, and to a method of capturing a 360xc2x0 surrounding panoramic scene.
2). Discussion of Related Art
Panoramic imaging arrangements have become popular in recent years for purposes of viewing 360xc2x0 surrounding panoramic scenes. Older generations of panoramic imaging arrangements generally consisted of revolving periscope-like constructions having relatively complex mechanisms for revolving them. More recently, stationary panoramic imaging arrangements have been developed. A stationary panoramic imaging arrangement generally has one or more lenses, each having a vertically extending axis of revolution, which are used to refract or reflect light received from a 360xc2x0 surrounding panoramic scene. The lenses alter the direction of the light, whereafter the light passes through a series of lenses which are located vertically one above the other and which further manipulate the light by, for example, focusing the light or altering the intensity of the light.
The task of receiving light in a sideways direction and altering the direction of the light so that the light then proceeds in a vertical direction is a difficult one. Altering the direction of light to such a degree, especially when coming from a 360xc2x0 surrounding scene, oftentimes leads to aberrations in the resulting light. These aberrations may include astigmatism of the light, defects in color of the light, a loss of image plane flatness, and other defects, some of which are discussed in more detail herein below.
Relatively complex lenses and lens arrangements have been developed in order to overcome these aberrations. Some of these lenses have surfaces which are aspherical (see for example U.S. Pat. No. 5,473,474 issued to Powell). Aspherical lenses are difficult to manufacture and therefore less practical to manufacture than for example spherical lenses.
One reason why aberrations in light occur is due to the use of refractive lenses instead of reflective lenses. The use of refractive lenses results in aberrations in color of the resulting light, whereas the use of reflective, or mirror lenses does not result in, or cause minimal aberrations in color of the light reflected from them. One reason for the lack of the use of reflective lenses, on the other hand, is that reflective lenses, when exposed to the environment, degrade through time, resulting in loss of image.
These and other aberrations in light are more prominent when light is received from a panoramic view at a relatively large lateral included angle, particularly if the included angle, in a vertical plane, is larger than 90xc2x0 and especially if the included angle extends from an angle below the horizon to an angle above the horizon, i.e. covering substantially more than a hemisphere.
According to one aspect of the invention, a panoramic imaging arrangement is provided comprising at least a first lens block including a convex reflective surface and a transparent lens. The convex reflective surface has a substantially vertical axis of revolution and is capable of receiving light from a 360xc2x0 surrounding panoramic scene, and reflecting the light for further manipulation. The transparent lens has a convex outer surface and covers the convex reflective surface. The convex reflective surface is thereby protected from environmental conditions which may otherwise result in damage to the convex reflective surface. An additional advantage is that a convex cover introduces fewer aberrations and internal reflections.
The convex reflective surface may, for ease of fabrication, be substantially spherical.
The transparent component may, for ease of fabrication, have a spherical outer surface thorough which light from the panoramic scene passes before reaching the convex reflective surface.
The panoramic imaging arrangement may include a second lens block secured to the first lens block. Light, reflected by the convex reflective surface, may pass through the transparent component, whereafter the light may pass through the second lens block. The second lens block provides a way for the first lens block to be held without obscuring its field of view.
The convex reflective surface is preferably capable of receiving light for an unbroken included angle of at least 60xc2x0 in a vertical plane, from the panoramic scene, and reflecting the light so as to pass through the second lens block.
The included angle preferably extends from an angle below the horizon to an angle above the horizon. The panoramic imaging arrangement is therefore capable of capturing more than just a hemispherical scene. The angle below the horizon is preferably at least 30xc2x0 below the horizon and the angle above the horizon is preferably at least 30xc2x0 above the horizon.
A transparent optical cement may be located between the first and second lens blocks and secure the first and second lens blocks to one another.
According to another aspect of the invention, a panoramic imaging arrangement is provided which includes at least a first lens block including a convex reflective surface and a transparent component. The convex reflective surface has a substantially vertical axis of revolution. The convex reflective surface is capable of receiving light from a 360xc2x0 surrounding panoramic scene for an unbroken included angle, in a vertical plane extending from an angle below the horizon to an angle above the horizon. The convex reflective surface is capable of reflecting the light for further manipulation. The transparent component covers the reflective surface.
According to a further aspect of the invention, a panoramic imaging arrangement is provided comprising at least one lens having a substantially vertical axis of revolution and a convex spherical reflective surface capable of receiving light from a 360xc2x0 surrounding panoramic scene and reflecting the light received from the panoramic scene. Reflective surfaces cause less aberrations in color, convex reflective lenses require less power, and spherical lenses are easier to manufacture.
Apparatus is preferably provided which is positioned to receive light reflected by the convex spherical reflective surface and is capable of correcting at least one aberration of the light.
The apparatus preferably manipulates the light so as to correct astigmatism, so as to do color correction, to focus the light, to adjust f-theta closer to a desired level, or so as to create a flat image plane when the light is focused.
The convex spherical reflective surface is preferably capable of receiving light for an unbroken included angle of at least 60xc2x0, in a vertical plane, whereafter the light from the entire included angle is received by the manipulation apparatus.
The included angle preferably extends from an angle below the horizon to an angle above the horizon.
According to a further aspect of the invention, a panoramic imaging arrangement is provided comprising at least one lens, and light manipulation apparatus. The lens has a substantially vertical axis of revolution. The lens is also capable of receiving light from a 360xc2x0 panoramic scene surrounding the lens for an unbroken included angle of at least 60xc2x0, in a vertical plane, extending from an angle below the horizon to an angle above the horizon. The lens is further capable of altering the direction of the light received from the panoramic scene. The light manipulation apparatus is positioned and capable of receiving light from the lens for the entire included angle. One advantage of such a lens is that a relatively large included angle, extending from below to above the horizon, can be viewed.
The lens preferably has a spherical surface altering the direction of the light.
The lens may have a reflective surface which reflects the light. The reflective surface may be convex and is preferably spherical.
According to yet a further aspect of the invention, apparatus is provided for capturing a panoramic scene. The apparatus comprises a vertical support structure, lower and upper lens blocks, and a convex reflective surface. The lower lens block is secured to an upper end of the support structure. The upper lens block is secured to the lower lens block in a position above the lower lens block and has a convex outer surface having a substantially vertical axis of revolution. The convex reflective surface is located on the upper lens block. Light from a 360xc2x0 surrounding panoramic scene is capable of passing through the convex outer surface of the upper lens block into the upper lens block, the light is then reflected off the convex reflective surface, and the light then passes through the upper lens block and then through the lower lens block. In such an apparatus there is little obscuring of the panoramic view by the support structure.
The apparatus for capturing the panoramic scene preferably includes a system of lenses positioned below the lower lens block to receive light after passing through the lower lens block.
According to yet a further aspect of the invention, a method is provided of mounting a panoramic lens arrangement including a first lens block which includes a convex reflective surface having a substantially vertical axis of revolution, and a transparent component covering the reflective surface, and a second lens block located on the first lens block. The method includes the step of securing the second lens block to a support structure in a position so that light from a 360xc2x0 surrounding panoramic scene passes through the transparent component, whereafter the light is reflected by the convex reflective surface, whereafter the light passes through the second block.
According to yet a further aspect of the invention, a method of capturing a panoramic scene is provided. Light, received from a 360xc2x0 panoramic scene surrounding a convex spherical reflective surface, is reflected from the convex spherical reflective surface. The light reflected from the convex spherical reflective surface may then be corrected for at least one characteristic of the light, the characteristic being selected from the group consisting of: astigmatism; color; f-theta and image flatness.
The convex spherical reflective surface preferably receives light for an unbroken included angle of at least 60xc2x0, in a vertical plane, whereafter the light from the entire included angle is corrected.
The included angle preferably extends from an angle below the horizon to an angle above the horizon.
According to yet a further aspect of the invention another method of capturing a panoramic scene is provided. Light is received from a 360xc2x0 surrounding panoramic scene for an unbroken included angle of at least 60xc2x0 extending from an angle below the horizon to an angle above the horizon. The direction of the light received from the panoramic scene is then altered. After the direction of the light is altered, at least one characteristic of the light is corrected, the characteristic being selected from the group consisting of: astigmatism; color; f-theta; and image flatness.